A wide-field spectroscopic survey of the cluster of galaxies Cl0024+1654 I. The catalogue(7)

We present the catalogue of a wide-field CFHT/WHT spectroscopic survey of the lensing cluster Cl0024+1654 at z=0.395. This catalogue contains 618 new spectra, of which 581 have identified redshifts. Adding redshifts available from the literature, the final

O.Czoskeetal.:SpectroscopicsurveyofCl0024:I.Thecatalogue

7

(a)

H/Hε

K

[OIII]

Hδ

HηHζGHγ

Hβ

(b)

skyHζHδ

G

HγHβ

MgI

KHHηHθ

(c)

[OIII]cr[OII]

Hβ

(d)

skyHδ

Hγ

cr

KH

G

Hβ

(e)cr

skybr

(f)

Hβ

br

MgI

G

cr

(g)

[OII]

[OIII]

sky

Hβ

Hη

Hε

Hγ

Hδ

Fig.2.Examplespectraandcorresponding15×15arcsec2sectionsfromtheCFH12kV-bandimage.ThecatalogueentriesfortheseobjectsarelistedatthetopofTable4.Spectra(a)and(d)arefromobservingrun2(CFHT),spectra(b),(c),(e)and(g)fromrun3(WHT),andspec-trum(f)isfromrun4(CFHT).Spectra(a),(b)and(c)areexamplesofspectrawith“secure/A”redshiftsbasedonalargenumberofemissionand/orabsorptionlines.Spectrum(d)isanexampleofa“probable/B”redshiftandspectrum (e)ofan“uncertain/D”redshift,basedonthe4000Abreakonly.Spectrum(f)isforthecentralgalaxyofthenortherngroupatz～0.495,discussedinSect.4.Spectrum(g), nally,isforaveryblueclustermembernearthecentreofCl0024+1654,showingalmostthecompleteBalmerseriesinemission.Cosmicrayhitsaremarked“cr”,skyemissionlinesby“sky”.Notethatthewavelengthrangesaredi erentineachpanel.equivalentwidthssothattheyarepositiveforemissionlines:NWλ=

intfi

i=1

fcwasestimatedas

themeanvaluewithintwowavelengthintervalsoneithersideoftheline;pixelswithvaluesmorethan3σawayfromthemeanlevelwereiterativelyrejectedinordertoavoidcosmicrayhitsinthecontinuumregion.Theautomaticmeasurementofthecontinuumlevelmakesitpossibletoestimateanerroronthecorrespondingequivalentwidths,thusallowinganassessmentofthedetectionsigni canceoftheline.ForthispurposewemodelthenoiseasPoisson-distributedphotonnoise.Thisallowsustorelatethevari-ancesonfiand

fc,S/N=

fc 2

=σ2

c/NcwhenaveragedoverNc

pixels.Addingtheerrorsduetofiand

N

2

(W+N(Wλ+Nint λ) λ+

int λ)2

λ

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